Conventionally, optical connectors for connecting an optical fiber having a circular cross section to a sheet-like optical waveguide have been disclosed. Such optical connectors have a first ferrule and a second ferrule that can be connected to each other with their connecting surfaces abutting against each other. Provided on the insertion surface that is on the side opposite to the connecting surface of the first ferrule is a first receptacle into which an optical fiber is inserted. An optical fiber is inserted into the first receptacle, and the optical fiber whose tip is brought into contact with the bottom of the first receptacle is held by the first receptacle. The second ferrule has a slit-shaped second receptacle that is a hollow extending from the insertion surface on the side opposite to the connecting surface into the body of the second ferrule. A sheet-like optical waveguide is inserted into the second receptacle, and the sheet-like optical waveguide whose tip is brought into contact with the bottom of the second receptacle is held by the second receptacle. The width and the height of the second receptacle are approximately the same as the width and the thickness of the optical waveguide, respectively.
The second ferrule may also have a third receptacle on the connecting surface, and a lens provided at the bottom of the third receptacle. While the first ferrule and the second ferrule are connected, light transmitted over the optical waveguide is collected at the lens, and the collected light enters the center of the optical fiber. A related art example is disclosed in Japanese Laid-open Patent Publication No. 2013-29782.
Misalignment among center lines of the optical waveguide, the lens, and the optical fiber reduces the efficiency of collection of light to the center of the optical fiber. For this reason, in the above-described optical connector, the second receptacle and the optical waveguide are designed to have substantially the same shape and size so that inserting the optical waveguide into the second receptacle matches the center lines of the lens and the optical waveguide with each other.
However, difficulty in controlling all of the width, the height, and the depth of the second receptacle with high accuracy leads to production of optical connectors in which the second receptacle is not formed as designed, and can result in reduction in the optical transmission efficiency at the optical connector. Removing the optical connectors that do not meet design requirements reduces a yield rate.